Patent GB-528055-A (GB)
Title: Improvements in machines for cutting gears
IPC: B23F5/28
Filed: 1939-04-20
Abstract: 528,055. Gear-cutting. GLEASON WORKS. April 20, 1939, No. 11958. Convention date, June 22, 1938. [Class 83 (iii)] In a machine for cutting gears, particularly by the methods described in Specifications 495,944 and 514,572, a cutter having a number of radially-arranged blades of concave profile is moved longitudinally of a tooth space in timed relation to its rotary movement so that different blades of the cutter cut at different points on the tooth space during a revolution of the cutter. The cutter is of the single cycle type with the teeth arranged part way round the periphery, the blank being stationary during cutting and being indexed when the gap in the cutter is opposite the blank. The machine bed has guide ways 31 for the cutter carriage 34 which carries, in ball bearings 41, a vertical spindle' 40 carrying the cutter C which preferably comprises a number of segments secured by screws 46. The profiles of the cutting edges are preferably of circular arcuate shape as described in the above-mentioned Specifications. Guideways 32 perpendicular to the guides 31 carry an adjustable base 50 having an inclined upper face carrying a complementary adjustable plate 60 on which the work-head 65 angularly adjustable around a pivot stud 66, is secured by bolts engaging in an arcuate T-slot. The head 65 carries a turret housing 75 fitted with a turret 76 which has three equi-spaced spindles 80 mounted in bearings 81 and each carrying an arbor 83 in which the blank is secured by a split collet 85 closed by a spring-urged draw-bar 87. The turret is intermittently indexed and when one spindle is in cutting position the others are at loading stations. The cutter is driven from a motor 90 through a coupling, bevel gearing 93, spur gearing 96, splined shaft 98, bevel gearing 100, and bevel gearing 103, 108. The reciprocation of the carriage 34 for moving the cutter along the teeth is effected from a cam 115, Fig. 24, having tracks 116, 117 which through followers 118, 121 impart positive movement to a bar 120, Fig. 6, adjustably connected to the carriage 34. The cam is mounted on a shaft 140 connected by gearing to the shaft 98 so that the cam is driven in timed relation with the cutter spindle. For bevel gears the direction of feed is inclined to the root surface of the tooth space and the cutters are of progressively varying height. To cushion the stroke of the carriage 34 a pinion 153 secured to the bar 120 works in a hydraulic cylinder 154 connected by ducts, to a reservoir 157, the ducts being normally closed by valves. On the movement to the right, Fig. 6, fluid escapes from the cylinder only through a metering valve of adjustable tension so that a load is put on the roller 118 to hold it against its cam. Each work spindle carries a notched index plate 150, Fig. 14, held during cutting by a locking dog 151 mounted on a stud 152 and urged into locking position by spring plungers 225. The index plates are secured to Geneva wheels 155. Only the spindle at the working station is indexed. For this purpose a cam 161 carrying a pin 160 co-acting with the Geneva wheel, actuates a block 163 secured to the locking dog to unlock the spindle. The cam and pin are carried by a shaft 169, Fig. 24, which is reciprocated by a cam 170 to move the cam 161 and pin 160 alternatively into and out of respective engagement with the locking dog and Geneva wheel. The shaft 169 is also rotated in timed relation with the cutter rotation by gearing, Fig. 24, operated from the shaft 98, the same train being connected by worm gearing 196 to the cam 170. The gearing is arranged so that when the gap 47 in the cutter is abreast of the blank the shaft 169 is moved forward so that the rotating arm 161 co-acts with the locking dog and dis-engages it, As the dog is unlocked, the pin 160 engages and drives the Geneva wheel through one pitch after which the cam allows the dog to relock the spindle. When indexing is thus completed the cam 170 shifts the shaft 169 and withdraws the pin and cam from their co-acting parts. A spring-pressed pin normally engages behind the block 163 and prevents accidental dis-engagement of the locking bolts. This pin is withdrawn at the required time by the mechanism which reciprocates the shaft 169. The turret is locked during cutting by a dog 235, Fig. 14, co-acting with notches 236 in a plate 237 and actuated by a piston 240 controlled by a valve 250. The turret is also clamped peripherally by means of tongues formed in the parts 270, 270<SP>1</SP> which have aligned bores in which a rod 274 carrying a coil spring 276 is mounted. The rod co-acts with a bell crank lever 278 which is rocked by a hydraulic cylinder 286 in one direction to clamp the periphery of the turret and in the other direction to release it. Rotation of the turret after unclamping and unlocking is effected by a rack 290, Fig. 25, actuated by a hydraulic cylinder 306 and connected through the turret through a gear 291, one-way pawl mechanism 295, Fig. 13, and spur gearing 302. Cam means are provided to control the exhaust from the cylinder 306 to control the turret rotation and avoid shocks. The cylinder 306 is controlled by a valve 310, Fig. 25, in parallel with the valve 25.0 controlling the locking dog, the valve 310 also controlling a piston 284 of the turret clamping mechanism. The valves 250, 310 are in turn controlled by pilot valves 360, 361. When a blank forming cycle has been completed, pressure is admitted to line 380 and flows through pilot valve 360 to valve 250 moving this valve downwards so that fluid flows to piston 240 and starts the turret indexing cycle. The valve 361 is moved in opposite directions by the piston 240 of locking dog 235 so that as the locking dog is withdrawn the valve 361 is moved to shift valve 310 and operate the piston of the turret rotating mechanism. The movements of valve 360 are controlled from the turret rotating mechanism through a pin and lever 376. Valves 385, 386, Fig. 25, prevent indexing of the turret until all the teeth of the gear are cut and the cutter is at the end of the stroke. The valve 385 is tripped by gearing driven from the feed cam. For this purpose the feed shaft 140, Fig. 24, is geared to a member 399 which rotates once while the blank is cut. When the last space is cut a lug 402 co-acts with a roller 403 and shifts the valve 385. At the same time a lever 405, Fig. 25, operates a switch 408 to break the circuit of the feed motor and stop the parts driven thereby. The motor is automatically restarted during the downward idle movement of the turretrotating rack 290. The valve 386 is operated by a cam 420, Fig. 25, on the shaft 140. This cam operates a lever 423 to move the valve 386 when the cutter is at the end of the return stroke. The valve 386 is thus operated at each revolution of the feed cam but the turret cannot be indexed until the valve 385 is also moved to the Fig. 25 position, indicating that the blank is completed and allowing fluid to pass into the line 430 which leads to further safety valves 435, 436 interposed in the line 380 leading to the pilot valve 360, Fig. 25, to ensure that the turret is not indexed unless the blanks are properly chucked at the loading stations. When the blanks are in the correct position, arms 440, 441 can be passed in front of the blanks at the two loading stations but if either blank is incorrectly chucked one of the valves 435, 436 cannot be shifted and fluid cannot pass to the line 380. When the arms 440, 441 are correctly swung past the blanks the valves 435, 436 are locked in the positions shown in Fig. 25 such locking means being disengaged when the turret rotating gear is actuated. The draw bars of the chucking mechanisms are actuated by rods 478 actuated at the loading stations by a pair of hydraulic cylinders 471 acting through rocker arms 475. To open the chucks at the loading stations fluid is admitted to lines 480, 481 controlled by a spring-closed valve 490 which is opened by pressure in the line 380, to allow fluid to pass to the cylinders 471 from lines 255 and 482. .Chips are removed by a conveyer comprising parallel chains 500, Fig. 20, connected by a series of scrapers or drags 512. The chains run on sprockets and the chips drop through an opening in the upper wall of the chain casing and fall on to the lower wall. After passing along the inclined part of the lower wall the chips are discharged to a receptacle at 520. The conveyer is actuated intermittently by ratchet mechanism 522 operated by a piston 526, Fig. 25, connected to the line 430 and to valve 385, the conveyer being thus advanced one step for each gear cut in the machine. A burr-removing attachment may be provided to trim up the completed gears. In one form, Fig. 26, each spindle is associated with a burrremoving tool T, which is secured in a holder 556 and mounted in a member 558 pivoted at 560 to the turret face. An arm 563 connected to member 558 co-acts with a spring plunger to hold the tool against the back cone of the gear. At the two non-cutting stations, the burrremoving tools are held in an inoperative position by cams 570. As the blank at the cutting station is indexed the space that has just been cut is moved past the tool which sweeps along the back cone surface and removes the burr. In a modified form, particularly for trimming pinions having a back surface of spherical shape, the tool T<SP>1</SP> Fig. 29, is ground to a complementary spherical shape and is of gapped ring form. The ring has recesses so that the completed gear may be pulled off the spindle. The tool is secured to a member fitting round the work collet 85. Springs urge the tool against the blank at the cutting station. A lever 600 pivoted at 601 has a semi-circular arm bearing at opposite points on a face of the holder. As the work spindle is indexed to a non-cutting station the end 607 of the lever rides up a cam rail 597 and dis-engages the burrremoving tool from th